Anaphylaxis is a “treat first” emergency. Anaphylaxis is a rapid, potentially fatal systemic hypersensitivity reaction. Airway swelling, bronchospasm, vasodilation, capillary leak, vomiting and shock can develop within minutes. Skin signs may be absent, especially in severe shock. Intramuscular adrenaline (epinephrine) into the anterolateral thigh is the first-line treatment; oxygen, positioning, airway support and fluids are added immediately. Antihistamines and steroids must never delay adrenaline. Use the current Uganda emergency protocol and senior clinical direction.
1. Learning objectives
- Define anaphylaxis and distinguish it from a mild allergic reaction and isolated asthma.
- Recognise airway, breathing, circulation, skin and gastrointestinal features, including presentations without rash.
- Perform immediate ABCDE assessment, safe positioning and rapid IM adrenaline administration.
- Describe oxygen, IV crystalloid, bronchodilator, glucagon and advanced airway support principles.
- Identify refractory, biphasic and fatal-risk features requiring observation or critical-care transfer.
- Provide patient education, trigger avoidance, adrenaline-device training, referral and documentation.
2. Definition and mechanism
Anaphylaxis is an acute systemic hypersensitivity reaction that can cause life-threatening airway, breathing or circulation compromise, usually with or without skin/mucosal changes. Mast cells and basophils release mediators such as histamine, tryptase and leukotrienes. These cause bronchoconstriction, laryngeal oedema, vasodilation, increased vascular permeability, urticaria, angio-oedema, vomiting and shock.
| Term | Meaning for emergency care |
|---|---|
| Allergen | A trigger such as food, medicine, insect venom, latex or a vaccine component that provokes hypersensitivity. |
| Allergic reaction | May be limited to itching, hives or local swelling; it becomes anaphylaxis when airway, breathing or circulation is compromised or severe multisystem involvement develops. |
| Anaphylactic shock | Circulatory collapse from vasodilation and capillary leak, often with bronchospasm or airway swelling. |
| Biphasic reaction | Recurrence after initial improvement without re-exposure; observation length depends on severity, treatment and risk factors. |
| Refractory anaphylaxis | Persistent airway, breathing or circulatory compromise despite repeated IM adrenaline and appropriate resuscitation; requires expert critical care. |
3. Common triggers and risk factors
- Foods: peanuts, tree nuts, milk, egg, fish, shellfish, sesame, fruits or locally common foods.
- Medicines: antibiotics, analgesics/NSAIDs, anaesthetic agents, vaccines, contrast media and herbal products.
- Insect venom: bees, wasps, ants and other stinging insects.
- Latex and occupational exposure: gloves, catheters and medical equipment.
- Exercise or co-factors: exertion, alcohol, infection, heat, NSAIDs or menstruation can lower the reaction threshold.
- Higher-risk patient: previous anaphylaxis, asthma (especially poorly controlled), mast-cell disease, cardiovascular disease, beta-blocker use, delayed access to care or remote living.
4. Clinical features
| System | Possible signs | Danger clues |
|---|---|---|
| Airway | Itchy throat, tongue/lip swelling, hoarse voice, stridor, difficulty swallowing, drooling. | Progressive voice change, stridor, inability to handle secretions or swelling of tongue/larynx. |
| Breathing | Wheeze, cough, chest tightness, tachypnoea, hypoxaemia, cyanosis. | Severe bronchospasm, silent chest, exhaustion, apnoea or falling consciousness. |
| Circulation | Flushing/pallor, tachycardia, dizziness, faintness, hypotension, collapse. | Weak/absent pulse, altered mental state, cold clammy skin and shock. |
| Skin/mucosa | Urticaria, itching, flushing, angio-oedema, conjunctival injection. | Absence of skin signs does not exclude severe anaphylaxis. |
| Gastrointestinal | Crampy abdominal pain, vomiting, diarrhoea, urge to defecate. | Repetitive vomiting with airway/breathing/circulation symptoms or sudden severe abdominal pain. |
| Neurologic | Anxiety, sense of doom, confusion, weakness, syncope. | Confusion, seizure or unconsciousness from hypoxia/shock. |
5. Clinical diagnosis and dangerous mimics
Diagnosis is clinical and should not wait for serum tryptase or other laboratory tests. Suspect anaphylaxis when a patient acutely develops airway or breathing compromise, or hypotension/end-organ symptoms, after a likely trigger. Skin/mucosal changes plus respiratory or cardiovascular symptoms strongly support the diagnosis.
- Asthma: wheeze without sudden allergen exposure, hives, angio-oedema or shock; however, anaphylaxis can present as severe bronchospasm.
- Vasovagal syncope: pallor, sweating, slow pulse and rapid recovery lying flat; anaphylaxis usually has tachycardia, wheeze, swelling or persistent shock.
- Panic attack: hyperventilation and tingling but no objective airway swelling, wheeze or hypotension.
- Sepsis: fever/infection pattern and slower progression; both can coexist.
- Foreign body, epiglottitis or croup: stridor but no multisystem allergic features; manage airway emergency.
- Angio-oedema from ACE inhibitors: may have isolated tongue/laryngeal swelling without urticaria; treat airway threat urgently and seek senior advice.
6. First five minutes: treat while assessing
- Call for help, bring the resuscitation trolley/oxygen and stop the suspected trigger if safe (stop an infusion, remove a stinger without squeezing, move away from food/latex).
- Lay the patient flat with legs elevated if tolerated. If breathing is difficult, allow sitting with legs outstretched. Place an unconscious patient in the recovery position; use left lateral positioning for a pregnant patient. Do not allow standing or walking.
- Give IM adrenaline immediately for airway, breathing or circulation features—do not wait for a rash, IV access or a doctor's arrival.
- Apply high-concentration oxygen for hypoxaemia, shock or severe distress; attach pulse oximetry, ECG and BP monitoring.
- Establish IV access, prepare crystalloid for hypotension and repeat ABCDE after every intervention.
7. Adrenaline (epinephrine): first-line medicine
Use the correct preparation and route. IM adrenaline 1 mg/mL (1:1000) in the anterolateral middle third of the thigh is the standard emergency route. Never delay for IV access. IV adrenaline boluses are hazardous and should be used only by experienced specialists in a monitored resuscitation setting.
| Patient group | Educational dose principle | Safety checks |
|---|---|---|
| Adults and adolescents | Follow local protocol; many resuscitation guidelines use 0.5 mg IM of 1 mg/mL (0.5 mL), repeated after about 5 minutes if airway/breathing/circulation compromise persists. | Confirm concentration, use the thigh, record time, reassess response and call senior support. |
| Children | Use a weight/age-based dose, commonly 0.01 mg/kg of 1 mg/mL up to the local maximum; use an approved auto-injector when that is the available device. | Do not copy adult volume; check weight/age chart and repeat according to protocol. |
| Pregnancy/older adult | Do not withhold indicated IM adrenaline. Position safely, provide oxygen and involve obstetric/medical support. | Monitor perfusion, ECG and response; maternal oxygenation is critical. |
- Use a new needle/syringe for each dose and inject through clothing only if necessary and safe.
- Reassess after 5 minutes; persistent compromise requires another IM dose and urgent critical-care help.
- Document trigger, dose, concentration, route, injection site, time and clinical response.
8. ABCDE emergency management
| Step | Assessment | Action |
|---|---|---|
| A – Airway | Tongue/lip swelling, hoarseness, stridor, drooling, inability to speak. | Call anaesthesia/airway expert early, prepare suction and difficult-airway equipment, give adrenaline; early intubation may be safer before swelling progresses. |
| B – Breathing | Wheeze, bronchospasm, SpO₂, respiratory rate, chest movement and fatigue. | Oxygen, repeat adrenaline if indicated, nebulised salbutamol for persistent bronchospasm, assist ventilation if tiring. |
| C – Circulation | Pulse, BP, capillary refill, skin, ECG, collapse and bleeding/other cause. | Supine positioning, IM adrenaline, rapid isotonic crystalloid for shock, large-bore IV/IO access and senior critical-care review. |
| D – Disability | AVPU/GCS, confusion, syncope, seizures and glucose. | Protect airway, check/treat glucose, continue oxygen and manage cardiac arrest if required. |
| E – Exposure | Hives, angio-oedema, trigger, medication/infusion site, pregnancy and injury from collapse. | Remove trigger, maintain warmth and dignity, search for medical alert information and record the suspected allergen. |
9. Fluids, bronchodilator and adjuncts
- IV crystalloid: give rapid weight/condition-appropriate boluses for hypotension or shock under protocol; reassess pulse, BP, capillary refill, lung signs and urine after each bolus.
- Bronchodilator: nebulised salbutamol is an adjunct for wheeze/bronchospasm; it does not replace adrenaline.
- Glucagon: consider for refractory hypotension/bronchospasm in a patient taking a beta-blocker, under senior direction; monitor for vomiting and aspiration.
- Antihistamines: non-sedating agents may relieve itch/urticaria after resuscitation but do not treat airway oedema, bronchospasm or shock.
- Corticosteroids: not first-line and should not delay adrenaline; use only when indicated by the clinician, such as refractory asthma or persistent allergic inflammation.
- Do not rely on: oral medicines in a shocked patient, subcutaneous adrenaline, nebulised adrenaline alone or prophylactic antibiotics.
10. Refractory anaphylaxis and advanced care
- Refractory disease means ongoing airway/breathing/circulation compromise after appropriate repeated IM adrenaline and fluids.
- Call critical care/anaesthesia, continue IM adrenaline while preparing a titrated IV adrenaline infusion by an experienced team, with continuous ECG/BP/SpO₂ monitoring.
- Use advanced airway support early if progressive laryngeal oedema, hypoxaemia, exhaustion or reduced consciousness develops; a surgical airway plan may be required.
- Manage cardiac arrest using the current resuscitation algorithm; continue to consider anaphylaxis as the reversible cause.
- Search for ongoing exposure, occult bleeding, myocardial infarction, tension pneumothorax or septic shock if the response is atypical.
11. Observation and biphasic reaction
| Risk pattern | Observation approach |
|---|---|
| Rapid, complete response to one IM dose and mild symptoms | Follow local risk-based observation policy; provide a responsible adult and clear return instructions. |
| More than one adrenaline dose, delayed treatment, severe respiratory/circulatory features or uncertain follow-up | Longer monitored observation/admission; many protocols use at least 4 hours after the last adrenaline dose, with longer observation for high-risk cases. |
| Refractory reaction, airway intervention, shock, severe asthma, pregnancy or major comorbidity | Admit to a monitored/critical-care setting and observe for recurrence and organ complications. |
Symptoms can recur after initial improvement without another exposure. A patient must not be discharged merely because the rash faded after antihistamine.
12. Nursing and EMT care plan
| Problem | Interventions | Evaluate |
|---|---|---|
| Airway oedema | Position safely, prepare airway equipment, call expert help, monitor voice/stridor and avoid delays. | Speech, swelling, stridor, oxygenation and airway patency. |
| Bronchospasm/hypoxaemia | Oxygen, nebulised bronchodilator, monitor SpO₂/respiratory effort and assist ventilation if needed. | SpO₂, air entry, respiratory rate, fatigue and blood gas where indicated. |
| Shock | Repeat IM adrenaline as indicated, IV/IO access, prescribed crystalloid, continuous ECG/BP and urine measurement. | Pulse quality, BP, capillary refill, mentation, urine and skin perfusion. |
| Anxiety/trauma | Stay with patient, explain steps, prevent standing/walking and provide privacy. | Cooperation, safety and ability to describe trigger/medicines. |
| Risk of recurrence | Observation, discharge plan, referral, allergy documentation and adrenaline-device training. | Stable observations, understanding of red flags and safe follow-up. |
13. Special populations
- Children: use weight/age-based adrenaline, keep them flat or held safely, involve caregivers and avoid frightening delays.
- Pregnancy: place in left lateral position when supine hypotension is a concern, give maternal oxygen/adrenaline promptly and involve obstetric services.
- Beta-blocker use: response to adrenaline may be blunted; early specialist support and glucagon consideration are important.
- Asthma: wheeze with sudden allergen exposure and shock is anaphylaxis until proven otherwise; adrenaline comes before routine asthma medicines.
- Older adults/cardiac disease: adrenaline is still lifesaving; monitor arrhythmia and ischemia while treating the allergic shock.
- Isolated angio-oedema: inspect the airway repeatedly; ACE-inhibitor angio-oedema may occur without hives and requires urgent airway planning.
14. Discharge, prevention and referral
- Document the suspected trigger, symptoms, medicines, adrenaline doses, response, observation period and final disposition.
- Provide a written emergency action plan and teach the patient/caregiver to recognise airway, breathing and circulation symptoms.
- Where prescribed and available, provide two adrenaline auto-injectors and demonstrate storage, expiry checking and thigh administration.
- Refer for allergy/immunology assessment, trigger investigation, vaccination/medicine review and management of asthma or mast-cell disease.
- Advise medical-alert identification and tell the patient to inform future clinicians, schools, workplaces, restaurants and caregivers.
- Teach avoidance without unsafe restriction; seek dietician support for food allergy and never rely on antihistamines alone for future anaphylaxis.
15. Clinical scenarios
Scenario 1 – post-injection collapse. Minutes after an antibiotic, a patient develops hives, wheeze, hoarseness and BP 70/40 mmHg. Stop the infusion, lay flat with legs elevated, give IM adrenaline immediately, oxygen, IV crystalloid and repeat ABCDE; call the resuscitation team and document the medicine/lot number.
Scenario 2 – anaphylaxis without rash. A patient suddenly becomes breathless, confused and hypotensive after eating, but the skin is normal. Treat as anaphylaxis; absence of urticaria does not exclude life-threatening airway/breathing/circulation compromise.
Scenario 3 – child with food reaction. A child has facial swelling, cough and vomiting after a peanut snack. Use weight-based IM adrenaline, keep the child flat/held safely, call emergency transport, repeat according to protocol if not improving and observe in hospital even if symptoms resolve.
Scenario 4 – wheeze mistaken for asthma. A known asthmatic has wheeze, facial flushing and faintness after a bee sting. Give adrenaline first, then bronchodilator for persistent wheeze; do not wait for a nebuliser to work.
16. Common errors to avoid
- Waiting for a rash, IV access, tryptase result or a doctor's arrival before giving IM adrenaline.
- Allowing a shocked patient to stand, walk or sit upright with legs dependent.
- Using antihistamines or steroids as substitutes for adrenaline.
- Giving IV adrenaline boluses outside an expert, fully monitored resuscitation setting.
- Failing to repeat adrenaline or fluids when airway/breathing/circulation compromise persists.
- Discharging immediately after symptom improvement without risk-based observation and an action plan.
- Not documenting the trigger and failing to report a medicine/vaccine reaction through the appropriate system.
ANAPHYLAXIS emergency check – “ADRENAL”
A – Assess airway, breathing and circulation
D – Do not delay IM adrenaline
R – Recline safely; never let the patient stand
E – Ensure oxygen, ECG, IV/IO access and escalation
N – Note trigger, dose, time and response
A – Add fluids/bronchodilator and expert airway support
L – Longer observation, learning and prevention plan
A – Assess airway, breathing and circulation
D – Do not delay IM adrenaline
R – Recline safely; never let the patient stand
E – Ensure oxygen, ECG, IV/IO access and escalation
N – Note trigger, dose, time and response
A – Add fluids/bronchodilator and expert airway support
L – Longer observation, learning and prevention plan
17. Revision questions
- Define anaphylaxis and list three systems that can be affected.
- Why is IM adrenaline the first-line treatment?
- Describe safe positioning for a conscious patient with breathing difficulty, an unconscious patient and a pregnant patient.
- List five signs of impending airway failure.
- When should IM adrenaline be repeated, and why is IV bolus adrenaline dangerous?
- Explain the roles and limitations of antihistamines, corticosteroids, salbutamol and glucagon.
- What factors require prolonged observation or admission?
- List six discharge/prevention measures after anaphylaxis.
18. Key take-home points
- Anaphylaxis is a clinical diagnosis and may occur without skin signs.
- Give IM adrenaline early in the anterolateral thigh for airway, breathing or circulation compromise.
- Lay the patient flat or position safely; do not allow standing or walking.
- Oxygen, IV crystalloid, bronchodilator and advanced airway support are adjuncts—not substitutes for adrenaline.
- Repeat assessment and adrenaline when compromise persists, and observe for biphasic recurrence.
- Every survivor needs a trigger plan, referral, education and documented allergy information.
Safety note: This is educational content for EMT students, not a prescription. Confirm adrenaline concentration, weight-based dose, repeat interval, observation period, fluid strategy and advanced-care decisions against the current Uganda emergency protocol and senior clinical supervision.
References for further study
- Resuscitation Council UK: Emergency treatment of anaphylaxis
- WHO: Brief overview of anaphylaxis as an adverse event following immunization
- ASCIA: Acute management of anaphylaxis
- ASCIA: First-aid plan for anaphylaxis
- Uganda Ministry of Health: current emergency-care, immunisation-safety and medicines-reaction guidance.